Telemetering system

ABSTRACT

A pipe installation system, the pipe string being composed of pipe sections which are added and removed to increase and decrease the length=of the drillpipe, and a length of cable is disposed within the drillpipe string and attached thereto by anchoring means. The anchoring means are deployable with the cable means and may be provided by a magnetic attraction or suction or the like between the anchoring means and he wall of the pipe, and means of removal of the cable and the anchoring means.

The present invention relates to a telemetering system, in particular,one disposed in a drillpipe.

The conventional manner of drilling a borehole comprises lowering adrill bit into the earth, the drill bit being powered, for instance, bythe rotation of the drillpipe, or by fluids circulating through thedrillpipe and thence back up to the surface through the space betweenthe drillpipe and the borehole. The drillpipe is made up of sections,new sections being added periodically at the top of the drillpipe stringto allow the drill bit to be lowered further.

Much useful data can be garnered from sensors included in the drillpipe,such as temperature and pressure. To retrieve this information at thesurface requires some form of media to transmit it through. Knownsystems include using pressure waves through the circulating mud, andelectromagnetic pulses. Better rates of transfer and less attenuationmay be achieved however by using an electrical conducting element.

The simplest way of installing a conducting cable, or indeed any line,along the drillpipe string is to wait until drilling has ceased andlower a single length down the drillpipe string. Where it necessary totake readings from instrumentation means before the drillpipe iscompleted however, the cable must be lowered into the drillpipe string,only to be withdrawn each time a new drillpipe section is added to thedrillpipe string.

One known method comprises a drillpipe incorporating conductingelements. The conducting elements of adjoining sections of drillpipe areelectrically connected by sliding contacts, Such a system is expensive,and liable to develop faults as a result of fluid contaminating theconnection. Many telemetry systems rely upon a segmented cable runningthrough the drillpipe, cable sections being added in order to allowfresh sections of drillpipe to be added.

Every connection between individual lengths of cable provides a furtheropportunity for faults to occur.

The object of the present invention is to provide an apparatus andmethod for disposing reliable telemetric equipment in drillpipes and thelike in an efficient manner.

According to the present invention there is provide a pipe installationsystem, the pipe string being composed of pipe sections which are addedand removed to increase and decrease the length of the pipe, wherein alength of cable is disposed within the pipe string, there being a cablestorage means for stowing the cable in a compact manner and paying outthe cable when the length of the pipe is increased such that the paidout cable is deployed in the increased length of pipe, wherein theanchoring means are provided which serve to attach the cable to aninside wall of the pipe following deployment of the cable in the pipe.

Preferably the anchors are attached to the cable at pore-determinedpositions a long the length of the cable. Preferably the anchorsposition themselves in an anchoring position as the cable is paid out.Preferably the anchors consist of a ring shaped wire which correspondapproximately to the inside diameter of the pipe.

Alternatively the anchoring means may be provided by the cable beingmagnetic and attaching itself to the inside wall of the pipemagnetically. Preferably the cable includes a sheath of effectivelypermanently magnetisable material, such as steel, the sheath beingmagnetised shortly before deployment. Alternatively the magneticattractiveness could be provided by a magnetic flexible tape attached tothe conductor or a complete outer layer. The anchoring means could alsobe provided by suction means.

Alternatively the anchoring means may be provided by the inside wall ofthe pipe and activated as the spool passes through the pipe.

Preferably the spool includes a cable feeder which guides the cable tothe desired position inside the pipe. Preferably this is against theinside wall of the pipe.

Preferably the cable store means is a bobbin upon which the cable iswound. The cable may include a wireless transmitter capable oftransmitting signals to a signal receiver. The cable is preferablyreleasably connected to a connector at its top, the cable beingdisconnected from the connector when a pipe section is to be added orremoved, threaded through the pipe section before being reconnected tothe connector, the cable including a wireless transmitter, such thatsignals carried by the cable can be transmitted by the wirelesstransmitter to be received by a signal receiving means.

According to a further aspect of the present invention, there isprovided a method of removing a cable installed along a pipe string orthe like, and fixed to the inside wall thereof by anchoring means, thepipe string being composed of pipe sections which are removed as theremoval of the pipe string progresses, a length of cable being disposedwithin the pipe string, a cable removing means being releasablyconnected to a connector at its top, the cable removing means beingadapted to remove the cable and the cable anchors.

The cable removal means preferably includes means for applying a solventto dissolve part of the cable or its anchoring means.

A telemetering system will now be described, by way of example only fora drill pipe and not intended to be limiting, with reference to thedrawings, of which;

FIG. 1 shows a longitudinal section of a drillpipe string installed inthe well at surface;

FIG. 2 shows an enlarged view of the top of the drill pipe of FIG. 1showing the connection means for the cable spool;

FIG. 3 shows an enlarged view of FIG. 1 in the region of the spool as asection of drill pipe is being deployed;

FIG. 4 shows a similar view to FIG. 3 with the spool in the position ofbeing anchored to a section of drill pipe;

FIG. 5 shows a similar view to FIG. 3 with the spool including a guidemeans for the cable and cable anchoring means arranged in the drillpipe;

FIG. 6 shows a similar view to FIG. 5 after the cable anchoring meanshaving been deployed;

FIG. 7 shows a similar view to FIG. 3 of an alternative embodiment ofthe anchoring mans provided by a magnetic means on the cable;

FIG. 7 a shows an embodiment of a magnetic means in the form of amagnetic tape;

FIG. 7 b shows an embodiment of the magnetic means in the form of amagnetic layer;

FIG. 7 c shows an embodiment of a magnetic means being provided bymagnetising a steel sheath around the cable;

FIGS. 7 d to 7 f show the attachment of the magnetic tape to the cableand the inside wall of the drill pipe;

FIG. 8 shows a the spool including ring shaped anchors arrangedintermittently along the length of the cable;

FIG. 9 shows a means of removal of the cable and anchors;

FIGS. 10 a to 10 d show an embodiment of a magnetic attaching means andits removal;

FIGS. 11 to 13 show an alternative embodiment of the use of a magneticanchoring means;

FIGS. 14 and 15 show a method of removal of the cable and anchoringmeans of the embodiment in FIGS. 11 to 13;

FIGS. 16 to 19 show a further embodiment of a magnetic fixing means forthe cable;

FIGS. 20 to 23 show the accomplishment of a wiper trip;

FIG. 24 is a cross section of a cable according to a further embodimentof the invention,

FIG. 25 is a longitudinal elevation of the cable of FIG. 24;

FIG. 26 shows a longitudinal section of the cable in FIG. 24 in thefitted position secured to the drill pipe;

FIG. 27 is a longitudinal section of a drill pipe including the cable ofFIG. 24 being installed;

FIG. 28 is a longitudinal section of another embodiment of the cablesystem installed in the drillpipe;

FIGS. 29 to 31 are longitudinal sections of this embodiment showingcable being installed;

FIGS. 32 to 35 are longitudinal sections of the grippers of thisembodiment in use;

FIGS. 36 to 39 are longitudinal sections of a another embodiment of thegrippers in use;

FIGS. 40 to 41 are longitudinal sections of a further embodiment of thegrippers in use; and

FIGS. 42 to 43 are longitudinal sections of this embodiment beingremoved.

FIG. 1 shows the drilling assembly 1 lowered into a well with a cablemodule 2 installed in the internal bore.

The drill assembly is advanced down the well by a top drive withstandard fluid entry above a goose neck 11 in the conventional way. Asshown in FIG. 2, the cable module is attached to a connection means in awinch assembly above the top drive. When the drill string's progressiondown the bore hole makes it necessary to add another pipe section to thedrill string, the cable module 2 is disconnected from the connectionmeans and allowed to rest upon an anchor 5 which holds it in positionagainst the drillpipe. The new pipe section is added to the existingdrillpipe, and the top drive and winch assembly connected to thedrillpipe. The winch means is ideally driven by an electric motor 13supplied through a slip ring assembly 15. Further details of theconnection means and winch assembly discussed in greater detail below.When the top drive is secured to the new pipe section, the connectionmeans are lowered through the new pipe assembly until they engage withthe cable module 2. The drill pipe proceeds downwards as the drillingprogresses and the cable module pays out the cable along the length ofthe drill pipe until the top end of the new pipe section is reached andthe process is repeated.

The method of data transfer between the stinger 8 and fishing socket 9of the cable module 2 is preferably by an inductive link. In this way,data may be continuously transmitted throughout the drilling process, byinduction when the fishing socket 9 is engaged or close to the stinger 8when the fishing socket are separated, and may transmit even when newdrill pipe sections are being added.

Referring to FIG. 3, an enlarged view of the cable module 2 is shown asa section of drill pipe is being deployed. The cable module includes astorage container 12 in which is stored the armoured cable to beinstalled in the drill pipe. The cable is fed out of the storagecontainer as it is pulled out with the running tool. Cable anchors 10are stored below the cable storage container 12 and arranged so thatafter a desired length of cable has been paid out an anchor will bereleased and will fall into position to anchor the cable against theupset of the inside wall of the drill pipe. In this embodiment theanchor is a ring shaped anchor corresponding to the inside diameter ofthe drill pipe and which grips the cable against an internal upset orrim 14 on the inside wall of the drill pipe normally present at thejoining point of the rill pipe section. The anchors could be arranged tobe deployed one for each length of drill pipe but it is preferably onlyrequired to deploy them at every 3 to 5 joints of drill pipe.

FIG. 4 shows a similar view to FIG. 3 with the spool module in theposition of being anchored to a section of drill pipe by anchors 5 whichact against the internal upset 14 at the lower joint of the lastconnected drill pipe section. Fluid flow is possible both through theinside of the module F2 through ports 16 in the stinger 8 and alsoaround the outside F1. This ensures that the drilling process cancontinue uninterrupted as new sections of drill pipe are added and thecable is paid out and anchored.

FIG. 5 shows further embodiment of the anchoring means for the cable tothe inside wall of the pipe. The same components have the samereferences and the spool module 2 includes a guide means 18 for feedingfor the cable to the desired position against the inside wall of thedrill pipe, and as in previous embodiments, fluid flow is both in theannulus around the spool holder and through a central bore of the spoolholder. In this embodiment a cable clamp is arranged at the joint of twocorresponding pipe sections and held open before being activated toengage the cable and grip it to the pipe section. A j-pin may be used tocorrectly orient the spool holder.

FIG. 6 shows a similar view to FIG. 5 after drill pipe has moveddownwardly and the cable anchoring means having been deployed, and thecable clamp has pivoted to retain the cable after the spool holder hasmoved past.

FIG. 7 shows a further embodiment of the anchoring means provided by amagnetic means on the cable. This embodiment also includes a feeder 18to push the cable against the inside wall of the drill pipe so that itbecomes attached by means of magnetism. In this case the cable guide orfeeder 18 would need to be made from a suitable non magnetic material,probably a suitable plastic.

FIG. 7 a shows one form of the magnetic means on the cable in the formof a flexible magnetic tape 22 which in this embodiment is adhered tothe steel casings 6 of the twin fibre optic cables 6 a. FIG. 7 b showsan embodiment of the magnetic means in the form of a magnetic layer 23completely surrounding the casing 6 of the fibre optic cable 6 a. Thetape and magnetic layer preferably consist of a permanently magneticmaterial.

FIG. 7 c shows an embodiment of a magnetic means being provided bymagnetising the steel casing or sheath 6 around a copper conductor 6 aby means of a magnetising coil 24 to effectively permanently magnetisethe steel casing. This can be carried out shortly before the cable ispaid out so that the magnetic effect doe not effect the handling of thecable up to that point but the cable will then affix itself to theinside wall of the steel drill pipe by means of its magnetic attraction.

FIGS. 7 d to 7 f show the attachment of the magnetic tape to the cableand the inside wall of the drill pipe. In FIG. 7 d a V shaped recess 23is formed in the tape 22 in which the cable 6 is pressed, and the Vshaped tape deforms around the curved outside surface of the cable 6.Ferrous particles 23 within the tape provide the required magneticallyattracting properties. Preferably, as shown in FIG. 7 e adhesive isapplied at the bottom of the V and this serves to secure the cable andmagnetic tape together. The flat surface of the magnetic tape is thenattracted and magnetically attaches to the inside wall of the drillpipe1.

FIG. 8 shows a the spool 2 including ring shaped anchors 26 arrangedintermittently along the length of the wound cable 6. The ring shapedanchors 26 are released as the cable is paid out (each anchor beingreleased as the spool portion beneath it is exhausted) and the anchors26 will become arranged concentrically within the drill pipe and restagainst the internal upset 14 of the drill pipe 1.

FIG. 9 shows a means of removal of the cable 6 and anchors 26. A cableremoving tool 30 is introduced into the well. The cable removing tool 30includes a battery pack 32 a storage bin 33, guide wheels, or walk downwheels 34 for driving the removing tool along the inside wall of thepipe, chopping means 36 to break up the cable and anchors into smallpieces and a cable gripping means 38 to grip the cable and feed it intothe removing tool.

FIGS. 10 a to 10 d show an embodiment of a magnetic attaching means andits removal. The original cable 6 having a fibre optic wire 6 a shown inFIG. 10 a is encased in a layer of extrudable magnetic material 19including a dissolvable metal component such as magnesium, shown in FIG.10 b. Such a layer could comprise particulate ferrous material,dispersed in magnesium and extruded around the outside of the cable.Thus when it is required to remove the cable acetic acid is pumped pastthe cable to rapidly dissolve the magnesium and so release the magneticparticles which disperse and are carried away by the mud, as shownprogressively occurring in FIGS. 10 c and 10 d.

FIGS. 11 to 13 show an alternative embodiment of the use of a magneticanchoring means. Separate magnets 40 are attached to the cable 6 byattaching means such as straps 42. In FIG. 12 a cable with the magnets40 already attached is being wound onto a bobbin 44 to formed the cablemodule 2, the feed spool being rotated in a perpendicular axis to thebobbin as shown by arrow a as the cable is wound onto the bobbin, sothat cable is not in a twisted state when it is paid out from thebobbin. The cable ma be also be sprayed with silicone in order toreleasably secure the cable in its wound configuration. The completedcable module 2 is shown in FIG. 13 with lengths of wound cableinterspersed with magnets housed in a thin-walled cylinder, the cablemodule including a cable guide 18 to urge the magnets into attractivecontact with the inside wall of the pipe 1.

FIGS. 14 and 15 show a method of removal of the cable and anchoringmeans of the embodiment in FIGS. 11 to 13. A winch line 51 with afishing hook 52 at the lower end of it is lowered into a pipe line inwhich the already installed cable is present attached by magneticattaching means. The fishing hook 52 latches onto the cable 6, 50,preferably at a fishing head provided on the cable or the anchoringmeans. After the cable 50 is disengaged from the spool assembly and thecable 50 above the spool assembly is peeled back away from the insidewall of the pipe 2 the upward force on the winch line is sufficient toovercome the magnetic attractive force of the anchoring means. The forcerequired to remove a single magnets, or small length of magnetic tape,by this ‘peeling’ technique is relatively small, and once separated fromthe wall of the drill pipe, the magnetic attraction is very much reducedand the line and magnets may be removed easily.

A further embodiment is shown in FIGS. 16 to 19, in which magneticelements are provided along the length of the cable to attach the cableto the inside wall of the pipe. In this embodiment the magnetic elementsare fitted to the cable as the cable is deployed and paid out from thespool. FIG. 16 shows the magnetic element 26 already attached to thecable 6 and secured thereto by means of an elastic element 61. Themagnetic element is provided in two parts 26 a and 26 b and before themagnetic element is deployed these two parts are held apart against theretaining force of the elastic element 61 by a holding rods 62. Theseholding rods extend along the entire length of a number of magneticelements corresponding ideally to the number desired to be deployed forthe entire length of cable provide on the spool. The cable also runsbetween the entire number of magnetic elements and is arranged betweenthe two holding rods 62 is the space provided by two semi-circulargrooves 63 one in each of the magnetic element parts 26 a, 26 b. When itis required to attach a magnetic element to the cable the rods 62 aremoved laterally away from the deploying end of the spool operatedautomatically by means of a motorised screw or the like, such that whenthe rods are free of the outermost magnetic element the two parts 62cease to be held apart by the rods 62 and are forced together by theelastic element 61 and so grip the cable 6 and are fixed to it.

The magnetic elements are guided to the inside wall of the pipe by theguide 18 so that the cable and the magnetic elements are out of the maineffect of the flow of fluids within the pipe and are also induced tomagnetically attach to the inside wall of the pipe.

Referring to FIG. 20 to 23, when a length of borehole has been drilledusing drillstring 1 having cable 6 paid out from a main spool 2 andanchored in the drillstring as described, the drillstring's operatorsmay anticipate that subsequent deeper lengths of borehole will requirewiper trips to be made to drill out unconsolidated rock material thatcaves in behind the drill bit. Referring to FIG. 21, before such alength x of borehole is begun, a secondary spool 65 having cable 76wound around it in the manner similar to that previously in respect ofthe main spool 2 is introduced into the drillstring, the cable 76 fromthe secondary spool 65 connecting to the top of the cable 6 from themain spool 2. As the drillstring progresses, as shown in FIG. 22, cable76 is paid out from the secondary spool 2, which is pulled through eachnew drillpipe section 73 by the winch and stinger 8 in a similar way tothat described for the main spool 2. The main spool 2 remains secured ina descending drillpipe section 72, and does not pay out further cable.

Before returning up the borehole to carry out the wiper trip, thesecondary spool 65 and the cable 76 previously paid out from thesecondary spool 65 can be recovered and disposed of, or alternativelythe secondary spool can wind its cable back onto itself. In general thesecondary spool's cable is conventional cable, though of course it toomay be anchored using the principles herein disclosed.

After the wiper trip has been completed, the main spool is situated atthe top of the borehole, as shown in FIG. 23. As it is often necessaryto complete several wiper trips over any one length of borehole (thoughof course this depends upon the characteristics of the rock), for eachsubsequent wiper trip a new secondary spool is installed in thedrillstring. In this way, the drillstring's operators can be assuredthat during these wiper trips the cable beneath the main spool issecured anchored. It is of course possible that after a wiper trip hasbeen completed, the main spool could be used once more to pay out cable(without using a secondary spool). But in general this is not envisaged.

Referring to FIGS. 24 to 27 a further embodiment of the invention isshown in which the cable comprises an outer material of an rubberised orelastomeric substance 66 comprising concave shapes or dimples 67 in itsouter surface which serve to provide a suckering effect between thecable and the inside wall of the drill pipe 1. In this embodiment thedimples 67 are provided on fours sides around the circumference of thecable 66 so as to provide a suction effect regardless of the orientationof the cable 66 and the dimples 67 are also located regularly along thelength of the cable 66.

FIG. 26 shows the cable 66 in position secured against the insidesurface of the drill pipe 1. Once establish the suction pressure will besubstantial as it will be increased by the increasing hydrostaticpressure as the drill pipe progresses down the well. In FIG. 27 it canbe seen that the rubber coated suction pad cable 66 is deployed in asimilar way to the previous embodiment with the guide 18 urging thecable 66 against the inside wall of the drill pipe 1 preferablyresulting in a pressing of the cable against the wall so that a littleair is urged out of the cavity formed by the concave dimple and the wallof the casing causing the suction effect as the elastomeric material ofthe wall of the cable recovers immediately following the release of thepressing effect by the guide 18.

Referring to FIG. 28 a cable 6 terminates at the bottom of the bore ofdrill string 1 as previously described. The cable extends up thedrillstring 1, being secured by grippers 70 located at regular intervalsalong the drillstring. In this embodiment, these grippers couldtypically be located in ever 1000 feet (though naturally this could bevaried, and will depend upon the type of cable; as in the firstembodiment, where armoured cable is employed, the grippers may be morefrequently deployed), so that for standard length drillpipe sections ofabout 30 foot, a gripper 70 will be located in every thirtieth drillpipesection. Additional cable is stored wound around a the spool of a cablemodule 2 of a which is suspended near the top of the drillstring.

The cable module and top of the drillstring is shown in more detail inFIG. 29. Each gripper 70 is attached to the inner bore of a drillpipesection 72 on a hinge 71. When the drillpipe section is made up on thedrillstring 1, the gripper 70 is in a retracted position as shown. Asfurther drillpipe sections are added, the cable module 2 is threadedthrough the newly added drillpipe sections using a fishing tool andwireline; as previously described, ratcheted supports allow the cablemodule to be dragged through drillpipe sections but resist the cablemodule passing downwardly past the internal upset of the drillpipesections. As the drillstring is extended, cable is paid out from thecable module, and guided to one side of the drillstring's bore by atongue 74. As for the previous embodiments, the cable module ideallyincludes a through path F2 so that drilling fluid is not impeded evenwhen the widest portions of the cable module are passing through thenarrowest portions of the drillstring's bore.

Referring to FIG. 30, when it is desired to secure the cable 6 to theside of the drillstring bore, the gripper 70 is activated so as to pivotthrough 90 degrees to a horizontal position. The wall of the drillpipesection opposite the grippers hinge has a concavity 75 arcuate inprofile, to accommodate the sweep of the gripper. The cable 6 issecurely pressed against the side of the drillpipe section by thegripper 70. Referring to FIG. 31, when the drillstring 1 is beingwithdrawn from the borehole and the individual drillpipe sections areremoved, the grippers 70 may be deactivated to release the cable 6.

The activation of the grippers may be achieved by hydrostatic means,i.e. by increasing the hydrostatic pressure in the well to particularlevels, of by other smart or remote means. Alternative methods will bedescribed below.

It will be realised that the gripper may be implemented or configured indifferent ways. Referring to FIG. 32, a gripper 80 is fitted inside adrillpipe section 72 secured by and pivoting upon a hinges 82 thatengage on opposite points across the circumference of the drillpipesection's bore; the internal profile of the drillpipe section 72 ismodified to accommodate the sweep of this gripper. As shown in FIG. 33,the cable 6 is threaded through the new drillpipe section 72 (thegripper is preferably shaped, for example in a C-shape, so as toaccommodate the passage of the cable module). Referring to FIG. 32, thegripper 80 is controlled by a fuse 84 constraining the gripper's hinge(which is biased by a spring to urge the gripper to rotate through anactivated position), which initially activates to pivot the gripper andgrip the cable on contact with drilling fluid. The fuse is ideally setto activate the gripper's pivoting after a set time period e.g. 30minutes, after the first contact with the drilling fluid. When it isdesired to release the cable, a set pressure (say 5000 psi) is appliedto the drillstring at the surface, and a piston 86 in the gripper causesa shear pin to fail as shown in FIG. 35, deactivating the gripper whichis then freed to pivot downwards, and releasing the cable 6 which maythen be winched up and recovered.

Referring to FIGS. 36 and 37, in an alternative embodiment a first fuse92 is situated at the gripping region of the gripper 90, which itinterlocks with a groove 93 on the inner surface of the drillpipesection 72. Once again, the cable 6 is introduced to the drillpipesection. The first fuse 92 may be composed of magnesium, so that itstarts to dissolve with components of the drilling fluid when thedrilling fluid comes into contact with the gripper 90. After a set timeperiod, say around 30 minutes, the first fuse 92 has dissolved to theextent that the gripper 90 is free to pivot into an activated positionand grip the cable against the inner wall of the drillpipe section, asshown in FIG. 38. Some or all of the gripper (or its pivoting supportpins) is composed of titanium. When it is desired to release the cable,fluoride is introduced into the circulating fluid, causing the titaniumto dissolve and the remaining parts of the gripper to falls away,releasing the cable as shown in FIG. 39.

Referring to FIG. 40, in a similar manner to previous embodiments, ahinged gripper 100 is located inside the drillpipe section 72. The hinge104 is spring-loaded, and biased to pivot to the horizontal position,but is held in a deactivated, vertical state by a fuse 102. The fuse 102is composed of magnesium, and dissolves after prolonged contact with thedrilling fluid (typically 30 minutes, though of course this can bevaried as desired). When the fuse has dissolved, the spring-loaded hinge104 pivots the gripper 100 to a vertical position as shown in FIG. 41,to anchor the cable 6 to the drillpipe section wall.

The gripper 100 shown in this embodiment is generally annular, with adiameter somewhat less than the internal diameter of the drillpipesection 72. Referring also to FIGS. 38 and 39, the annular gripper 100includes a gripping surface 106 an the outside edge of the gripper, onthe portion of the gripper opposite the gripper's hinge 104, whichengages with the cable 6 and urges it securely against the side of thedrillpipe section 72. Also provided by the gripper at this region is arelease arm 105, which comprises an arm set upon a hinge 109 upon thegripper, the distal end of the arm extend towards the centre of thedrillpipe section's bore. On the other side of the hinge 109 issupported a cutter 107 and a resilient gripper hook 108. Referring toFIG. 38, in order to release the cable 6 from the gripper, a wiper plug110 is introduced to and pumped down the drillstring 1. As the wiperplug 110 passes through the gripper 100, it engages the release arm 105,causing it to pivot, thereby cutting the cable 6 at the point at whichit is anchored, and the resilient gripping hook 108 re-anchors the cable6 beneath the cut. The cable 6 above the gripper may now be retrieved.

In this manner the cable may be retrieved in manageable sections(ideally 1000 to 2000 feet long), as opposed to a single long length ofcable (say 20,000 feet) which is prone to becoming snarled and knotted.It can be easily detected when the wiper plug has reached the gripper(since the lower end of the cable no longer be secured), and the pumpingof the plug may then be paused until enough drillstring has been removedto access the drillpipe section having the topmost gripper. The top ofthe next section of cable may then be held whilst the cable is severedat the next gripper.

It will be seen that by securing cable (whether conductive cable,fibre-optic cable or some other type) the cable does not have to supportits entire weight, and so need not be engineer to be as rugged andexpensive as if such securement were not used but without the risk thatthe cable will break through the tension it experiences. Should thecable nevertheless break, problems due to snarled knotted lengths ofcable (known as ‘bird's nests’) will be minimised since most of thelength of the cable will remain secured by the grippers, and only anindividual length between two consecutive grippers will be involved.

Alternative embodiments using the principles disclosed will suggestthemselves to those skilled in the art, and it is intended that suchalternatives are included within the scope of the invention, the scopeof the invention being limited only by the claims.

1. A pipe installation system, the pipe-line being composed of pipesections which are added and removed to increase and decrease the lengthof the pipe, wherein a length of cable is disposed within the pipe,there being a cable storage means for stowing the cable in a compactmanner and paying out the cable when the length of the pipe is increasedsuch that the paid out cable is deployed in the increased length ofpipe, wherein the anchoring means are provided which serve to attach thecable to an inside wall of the pipe following deployment of the cable inthe pipe.
 2. A pipe installation system according to claim 1, in whichthe anchors are attached to the cable at pore-determined positions along the length of the cable.
 3. A pipe installation system according toclaim 2, wherein the anchors position themselves in an anchoringposition as the cable is paid out.
 4. A pipe installation systemaccording to claim 2, wherein the anchors consist of a ring shaped wirewhich correspond approximately to the inside diameter of the pipe.
 5. Apipe installation system according to claim 1, wherein the anchoringmeans is provided by the cable having magnetic elements attached to itat intermittent points along its length to attach the cable to theinside wall of the pipe magnetically.
 6. A pipe installation systemaccording to claim 1, wherein the cable includes a sheath of effectivelypermanently magnetisable material, such as steel, the sheath beingmagnetised shortly before deployment.
 7. A pipe installation systemaccording to claim 1, wherein the magnetic attractiveness is provided bya magnetic flexible tape attached to the conductor or a complete outerlayer.
 8. A pipe installation system according to claim 1, wherein theanchoring means may be provided by the inside wall of the pipe andactivated as the spool passes through the pipe.
 9. A pipe installationsystem according to claim 1, wherein the anchoring means is provided bythe cable having suction elements attached to it at intermittent pointsalong its length to attach the cable to the inside wall of the pipe bymeans of suction.
 10. A pipe installation system according to claim 1,wherein the spool includes a cable feeder which guides the cable to thedesired position inside the pipe.
 11. A pipe installation systemaccording to claim 1, wherein cable is guided against the inside wall ofthe pipe.
 12. A pipe installation system according to claim 1, whereinthe cable store means is a bobbin upon which the cable is wound.
 13. Apipe installation system according to claim 1, wherein the cableincludes a wireless transmitter capable of transmitting signals to asignal receiver.
 14. A pipe installation system according to claim 1,wherein the cable is releasably connected to a connector at its top, thecable being disconnected from the connector when a pipe section is to beadded or removed, threaded through the pipe section before beingreconnected to the connector, the cable including a wirelesstransmitter, such that signals carried by the cable can be transmittedby the wireless transmitter to be received by a signal receiving means.15. A method of installing pipe sections to form a pipe includinginstallation of a continuous cable within the installed pipe comprising:supporting a continuous length of cable arranged on a spool which isreleasably connectable to a tension line within the pipe, resting thespool on support means within the pipe, disconnecting the tension linefrom the spool, and adding a new pipe section, reconnecting the tensionline to the spool to support the spool as the new pipe section isprogressively fitted, paying out of the cable from the spool.
 16. Amethod according to claim 14 characterised in that the cable transmitsdata to surface whilst the spool is connected to the tension line.
 17. Amethod according to claim 15, wherein data is transmitted from the cableto the surface whilst the spool is disconnected from the tension line bymeans of a radio frequency connection.
 18. A pipe installation system,wherein there is provided a method of removing a cable installed along apipe string or the like and fixed to the inside wall thereof byanchoring means, the pipe string-being composed of pipe sections whichare removed as the removal of the pipe string progresses, a length ofcable being disposed within the pipe string, a cable removing meansbeing releasably connected to a connector at its top, the cable removingmeans being adapted to remove the cable and the cable anchoring means.19. A pipe installation system according to claim 17, wherein the cableremoval means preferably includes means for applying a solvent todissolve part of the cable or its anchoring means.